Abstract
This study presents the effect of aqueous Pb(II) and nutrient concentrations on the Pb(II)-removal, biomass viability, active species identities, and population distribution of an industrial Pb(II) resistant microbial consortium. The studied consortium has previously shown to be highly effective at precipitating Pb(II) from solution. At all conditions tested (80 and 500 ppm Pb(II), and varying nutrients conditions) it was found that circa 50% of Pb(II) was removed within the first 3 h, with the absence of any visual changes, followed by a slower rate of Pb(II) removal accompanied by the formation of a dark precipitate. The Pb(II) removal was found to be independent of microbial growth, while growth was observed dependent on the concentration of Pb(II), nutrients, and nitrates in the system. SEM analysis indicated viable bacilli embedded in precipitate. These findings indicate that precipitation occurs on the surface of the biomass as opposed to an internal excretion mechanism. BLAST (Basic Local Alignment Search Tool) results indicated Klebsiella pneumoniae as the active species responsible for Pb(II) bioprecipitation for both the 80 and 500 ppm isolated colonies, while a diverse population distribution of organisms was observed for the streak plate analyses. A quicker microbial generation rate was observed than what was expected for Klebsiella pneumoniae, indicating that the overall consortial population contributed to the growth rates observed. This study provided insights into the factors affecting Pb(II) bio-removal and bioprecipitation by the investigated industrially obtained consortium, thereby providing invaluable knowledge required for industrial application.
Highlights
Lead (Pb) is an abundant and pernicious environmental contaminant posing significant human health risks; the maximum safe concentration of Pb in drinking water is estimated at 0.01 ppm [1]
The study investigated the effect of Pb(II) and nutrient concentrations on Pb(II) bio-removal, microbial growth, active species, and population distribution of an industrially obtained Pb(II)-resistant consortium
The results demonstrated that the removal of Pb(II) from solution was independent of microbial metabolic activity and nutrient availability; the majority of Pb(II) removal (≈50%) took place during the first 3 h in the absence of observable changes in reactor medium, indicating a biosorption mechanism present
Summary
Lead (Pb) is an abundant and pernicious environmental contaminant posing significant human health risks; the maximum safe concentration of Pb in drinking water is estimated at 0.01 ppm [1]. Serious human health risks include immunological, neurological, cardiovascular, reproductive, as well as developmental impacts [2]. The recovery of Pb, as opposed to the mere removal of Pb from the environment, is of prime interest as the United States Geological Survey estimates that only 17 years’ supply of global raw workable Pb reserves is available [3]. Various microorganisms have exhibited the capacity to remediate Pb(II) from polluted environments with the aid of various methods by reducing the mobility and bioavailability of Pb(II), including bioaccumulation, surface biosorption, extracellular sequestration, and bioprecipitation [5].
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